Interestingly, introduction of this disulfide bond did cause large increase in the stability of the ACE2 protease domain, indicated by the Tm shift of +12.5, +7.0, and +11.5 degrees for WT, 3N39, and 3N39v2 ACE2, respectively (Fig. 2e), suggesting the potential benefit of this mutation in formulating the anti-COVID-19 therapeutics. The gene discussed is ACE2; the disease is COVID-19.